The present invention relates to the management of resources in a communication system.
It finds a particular, although nonexclusive, application in a communication system of UMTS (“Universal Mobile Telecommunication System”) type, using a functionality for transmitting information at high-throughput of the “FDD enhanced uplink” type.
The “FDD enhanced uplink”, which is currently the subject of a standardization, is in particular described in technical specification TS 25.309, V0.2.0, “FDD Enhanced Uplink; Overall description; Stage 2 (Release 6)”, published in June 2004, by the 3GPP (“3rd Generation Partnership Project”). This functionality makes it possible in particular to transmit information at high-throughput from a radio terminal (or UE, for “User Equipment”) to one or more base stations (or “Node B”), on a dedicated transport channel called E-DCH (“Enhanced—Dedicated CHannel”).
One of the specificities of the “FDD enhanced uplink” resides in the possibility, for each base station, of directly controlling the communication resources on the E-DCH, within certain limits fixed by the radio network controller (RNC). This possibility is designated by “Node B controlled scheduling” in the aforesaid technical specification TS 25.309.
Such operation differs from the management of the other communication resources, as for the conventional dedicated channels and the common channels, where it is the RNC that determines the resources to be used for each UE, possibly after negotiation with the latter.
The controlling of the E-DCH resources by the Node B makes it possible to take into account parameters available at the level of this Node B, such as an interference level estimated on the uplink channels. One thus ensures that the transmissions performed by the UEs on respective E-DCH channels do not generate interference beyond a predetermined level.
Another exemplary parameter that can be taken into account in the controlling of the resources by the Node B is the reception capacity of this Node B, that is to say the maximum throughput at reception that this Node B is capable of processing. Specifically, certain operations are performed on the signals received by a Node B to retrieve the information that they carry, such as a despreading and a decoding in particular. To conduct these operations in an effective manner, it can therefore be useful to limit the amount of information received at the Node B.
By way of example, if a Node B has a reception capacity of 6 Mbit/s and if the information transmitted on the common and dedicated uplink channels (other than the E-DCHs) bound for this Node B already represents an aggregate throughput of 2 Mbit/s, it is desirable that the sum of the transmission throughputs on all the E-DCHs bound for this Node B, each corresponding to a UE, be less than or equal to 4 Mbit/s (=6−2 Mbit/s), lest it not be possible effectively to carry out the processing operations required at the Node B and thus not retrieve all the information transmitted by the UEs.
It therefore turns out to be necessary to indicate to each UE capable of communicating on an E-DCH channel bound for a Node B, the maximum throughput that this UE is permitted to use for transmission. In the above example, if two UEs use the “FDD enhanced uplink” functionality, the Node B can request them to limit their transmission throughput to 2 Mbit/s each, or else to 4 Mbit/s for one and 0 Mbit/s for the other for example.
Given that the Node B can choose to assign a different maximum throughput for each UE, it is then appropriate to indicate this throughput to each UE in an individual manner, for example on a respective dedicated channel. However, such a mechanism is itself ressource greedy. If the information of maximum throughput to be used is transmitted by puncturing of bits on a downlink traffic channel, that is to say by replacing certain useful data bits by said information of maximum throughput, this mechanism can furthermore degrade the reception of the information transmitted on this downlink channel.
This phenomenon is accentuated by the fact that the communication resources used for the channels other than the E-DCHs, that is to say the conventional dedicated and common uplink channels, are assigned in a prior manner by the RNC. But, the use of the resources varies, in particular on the dedicated channels, so that the bandwidth available to the Node B for receiving information, within the limit of the capacities of the Node B, changes in the course of time. If one wants to profit from a maximum of throughput on the E-DCH channels, it would therefore be advisable to regularly update the throughput thresholds not to be exceeded for each UE. The signalling resulting therefrom, for example on downlink dedicated channels, can then pose a problem.
This said, neither is it desirable to limit the updates of the throughput thresholds to be applied by each UE so as to avoid overly significant signalling, since this would lead either to unnecessary restriction of the throughput and the capacity on the E-DCH channels in the case where the fixed throughput thresholds are too low, this being contrary to their objective, or to enduring degradation of the quality of reception in the case where the fixed throughput thresholds are too high.
Another problem appears furthermore when a UE is capable of transmitting data on an E-DCH channel bound for several Nodes B simultaneously, that is to say when this UE is in a macrodiversity (or “soft handover”) situation.
In this case specifically, each Node B of the active set with which the UE communicates possesses its own inherent criteria, both in terms of measured interference and of reception capacity. The management of E-DCH resources being delocalized at the level of the Node B as indicated above, it is then possible that each Node B transmits to the UE a different throughput threshold not to be exceeded, without consultation with the other Nodes B of the active set. It is thus difficult for the UE to obtain the entirety of the threshold information on the part of the various Nodes B and to determine the maximum throughput that it must ultimately apply on the basis of the information received.
An object of the present invention is to alleviate the drawbacks mentioned above, by proposing management of the resources which achieves a good compromise between transmission throughput and quality of reception.
Another object of the invention is to have effective management of the resources even in a macrodiversity situation.